(function(){

  class Animal{
    name: string;

    constructor(name:string ){
      this.name = name;
    }
    sayHello(){
      console.log('动物在叫');
    }
  }

  class Dog extends Animal{

    age:number;

    constructor(name:string , age:number){
      // 如果子类中写了构造函数，在子类构造函数中必须对父类的构造函数进行调用
      super(name);
      this.age = age
    }

    sayHello(){
      // super表示当前类的父类
      super.sayHello
    }
  }

  const dog = new Dog('旺财',3)
  dog.sayHello()

})()